Updated Security researcher @dfirblog has discovered what he calls a devastating flaw in Windows' Kerberos authentication system.
The flaw cannot be fixed and the only solution is to introduce and use Microsoft's Credential Guard program to prevent passwords from being stored in memory, according to his extensive
blog post.
The flaw results from how the third-party authentication system creates secret keys: by using the password associated with a disabled username (krbtgt). That password is rarely changed, making it possible to bypass the authentication system altogether and allow an attacker to grant themselves admin privileges, as well as create secret passwords for existing users and new users that don't exist.
Although some of the entry points are time-limited – the system will seek to validate accounts after 20 minutes – because it is possible to create fake users without limit, it is possible to access a system incessantly.
